Comoving-frame radiative transfer in arbitrary velocity fields

II. Large scale applications

¹ Hamburger Sternwarte, Gojenbergsweg 112, 21029 Hamburg, Germany e-mail: [sknop;yeti]@hs.uni-hamburg.de
² Homer L. Dodge Department of Physics and Astronomy, University of Oklahoma, 440 W Brooks, Rm 100, Norman, OK 73019, USA e-mail: baron@ou.edu
³ Computational Research Division, Lawrence Berkeley National Laboratory, MS 50F-1650, 1 Cyclotron Rd, Berkeley, CA 94720, USA

Received: 4 February 2009
Accepted: 18 March 2009

Abstract

Aims. A solution of the radiative-transfer problem in arbitrary velocity fields introduced in a previous paper, has limitations in its applicability. For large-scale applications, the methods described also require large memory sets that are commonly not available to state-of-the-art computing hardware. In this work, we modify the algorithm to allow the computation of large-scale problems.

Methods. We reduce the memory footprint via a domain decomposition. By introducing iterative Gauss-Seidel type solvers, we improve the speed of the overall computation. Because of the domain decomposition, the new algorithm requires the use of parallel-computing systems.

Results. The algorithm that we present permits large-scale solutions of radiative-transfer problems that include arbitrary wavelength couplings. In addition, we discover a quasi-analytic formal solution of the radiative transfer that significantly improves the overall computation speed. More importantly, this method ensures that our algorithm can be applied to multi-dimensional Lagrangian radiative-transfer calculations. In multi-dimensional atmospheres, velocity fields are in general chaotic ensuring that the inclusion of arbitrary wavelength couplings are mandatory.